The present invention relates to a hot steel cutting apparatus and, more particularly, to an apparatus for continuously detecting flaws in the hot steel material and cutting the material in a predetermined length including an accurately estimated length loss due to conditioning.
A hot continuous cast steel piece (approximately 800.degree. C.) produced by a continuous casting apparatus is cut by a gas flame into slabs of a length suitable for the succeeding step, and, after being cooled, is subjected to cold inspection and cold conditioning. The conditioned slabs are heated to high temperatures of about 1200.degree. C. in a heating furnace and rolled by a plate mill or a hot rolling mill into products.
The thermal waste caused by the fact that the produced slabs at nearly 800.degree. C. are cooled to room temperature and again heated to about 1200.degree. C. has heretofore been unavoidable because there was no effective method for flaw inspection and partial conditioning of hot steel.
The slabs have heretofore been cut by a gas flame into a predetermined length including a uniform length to allow for loss due to conditioning in order to obtain the required dimensions of the hot rolled steel plates on the assumption that all the slabs required cold conditioning. Even in a slab free of flaws, after it has been processed into a hot rolled plate, since the length uniformly preestimated as loss due to conditioning has been cut away and discarded, the yield has been the same as in slabs having flaws. Such a wasteful slab length determination has been inevitable because a method for flaw inspection of hot steel has not yet been developed. In other words, inability to obtain an accurate estimation of the loss of length due to conditioning has been a major factor preventing an increase in the yield.